netdev - RE: [PATCH net-next] tipc: delete tipc_mtu_bad from tipc_udp

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Date: Tue, 30 May 2023 06:06:01 +0000
From: Tung Quang Nguyen <tung.q.nguyen@...tech.com.au>
To: Xin Long <lucien.xin@...il.com>, network dev <netdev@...r.kernel.org>,
	"tipc-discussion@...ts.sourceforge.net"
	<tipc-discussion@...ts.sourceforge.net>
CC: "davem@...emloft.net" <davem@...emloft.net>, "kuba@...nel.org"
	<kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>, Jon Maloy <jmaloy@...hat.com>
Subject: RE: [PATCH net-next] tipc: delete tipc_mtu_bad from tipc_udp_enable

>Subject: [PATCH net-next] tipc: delete tipc_mtu_bad from tipc_udp_enable
>
>Since commit a4dfa72d0acd ("tipc: set default MTU for UDP media"), it's
>been no longer using dev->mtu for b->mtu, and the issue described in
>commit 3de81b758853 ("tipc: check minimum bearer MTU") doesn't exist
>in UDP bearer any more.
>
>Besides, dev->mtu can still be changed to a too small mtu after the UDP
>bearer is created even with tipc_mtu_bad() check in tipc_udp_enable().
>Note that NETDEV_CHANGEMTU event processing in tipc_l2_device_event()
>doesn't really work for UDP bearer.
>
>So this patch deletes the unnecessary tipc_mtu_bad from tipc_udp_enable.
>
>Signed-off-by: Xin Long <lucien.xin@...il.com>
>---
> net/tipc/bearer.c    | 4 ++--
> net/tipc/bearer.h    | 4 ++--
> net/tipc/udp_media.c | 4 ----
> 3 files changed, 4 insertions(+), 8 deletions(-)
>
>diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
>index 53881406e200..114140c49108 100644
>--- a/net/tipc/bearer.c
>+++ b/net/tipc/bearer.c
>@@ -431,7 +431,7 @@ int tipc_enable_l2_media(struct net *net, struct tipc_bearer *b,
> 	dev = dev_get_by_name(net, dev_name);
> 	if (!dev)
> 		return -ENODEV;
>-	if (tipc_mtu_bad(dev, 0)) {
>+	if (tipc_mtu_bad(dev)) {
> 		dev_put(dev);
> 		return -EINVAL;
> 	}
>@@ -708,7 +708,7 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
> 		test_and_set_bit_lock(0, &b->up);
> 		break;
> 	case NETDEV_CHANGEMTU:
>-		if (tipc_mtu_bad(dev, 0)) {
>+		if (tipc_mtu_bad(dev)) {
> 			bearer_disable(net, b);
> 			break;
> 		}
>diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
>index bd0cc5c287ef..1ee60649bd17 100644
>--- a/net/tipc/bearer.h
>+++ b/net/tipc/bearer.h
>@@ -257,9 +257,9 @@ static inline void tipc_loopback_trace(struct net *net,
> }
>
> /* check if device MTU is too low for tipc headers */
>-static inline bool tipc_mtu_bad(struct net_device *dev, unsigned int reserve)
>+static inline bool tipc_mtu_bad(struct net_device *dev)
> {
>-	if (dev->mtu >= TIPC_MIN_BEARER_MTU + reserve)
>+	if (dev->mtu >= TIPC_MIN_BEARER_MTU)
> 		return false;
> 	netdev_warn(dev, "MTU too low for tipc bearer\n");
> 	return true;
>diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
>index 0a85244fd618..926232557e77 100644
>--- a/net/tipc/udp_media.c
>+++ b/net/tipc/udp_media.c
>@@ -739,10 +739,6 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b,
> 		udp_conf.use_udp_checksums = false;
> 		ub->ifindex = dev->ifindex;
> 		b->encap_hlen = sizeof(struct iphdr) + sizeof(struct udphdr);
>-		if (tipc_mtu_bad(dev, b->encap_hlen)) {
>-			err = -EINVAL;
>-			goto err;
>-		}
> 		b->mtu = b->media->mtu;
> #if IS_ENABLED(CONFIG_IPV6)
> 	} else if (local.proto == htons(ETH_P_IPV6)) {
>--
>2.39.1
Reviewed-by: Tung Nguyen <tung.q.nguyen@...tech.com.au>